This invention relates to a device for frictionally engaging an end of a workpiece such as a board on a moving lugged chain conveyor and laterally translating the workpiece perpendicularly relative to the direction of travel so as to accurately reposition the workpiece in relation to downstream work centres such as trimming saws, without impeding the downstream travel rate of the workpiece.
Lumber within a mill is generally transported by transfer chains having upstanding lugs or like means for engaging and moving lumber workpieces. Such transfer chains can now commonly travel at a rate of, for example, up to 200 lugs per minute.
As taught in the prior art, as a board is transported toward a trimmer gang saw for example, sensors determine the position of the a board in relation to the position of the saws in the gang saw. The final positioning of the board for accurate trimming is attempted by, in one method, actively positioning a fence against which the board has been ended. At high transfer rates it is undesirable to have to end the board against a fence because inaccuracy is introduced, for example, because of bounce-back of the board to name just one disadvantage. Inaccuracy is the result of having to reposition the board across the moving chains in the time interval allowed by the lug spacing along the chains.
It is one object of this invention to provide a workpiece repositioning device that may quickly and more accurately reposition a lumber workpiece in relation to a downstream workstation or machine or work centre such as a trimmer, without impeding the rate of travel of the workpieces, and so as to allow the longitudinal translation of the workpiece along its length while the workpiece is firmly in contact with the lugged transfer chain.
In summary, the present invention is an apparatus for repositioning a workpiece on a lugged conveyor, where the conveyor has lugs for carrying the workpiece spaced apart by a lug space in a downstream direction. The apparatus includes a sensor for detecting the position of the workpiece on the conveyor and relaying position information to a processor, at least one running element mountable or mounted in cooperation with the conveyor, a selectively actuable actuator cooperating with the processor for the selective actuation of the running element.
The running element may be disposed on one side of a workpiece flow path on the conveyor. The running element frictionally engages a workpiece as the workpiece translates downstream in a first direction along the flow path on the conveyor. On the conveyor the workpiece is oriented so that its longitudinal axis is substantially perpendicular to the first direction. The running element is mounted so that it does not move in the first direction. The running element is selectively actuable so as to selectively translate the workpiece, when in frictional engagement therewith, in a second direction substantially perpendicular to the first direction.
The running element in actuated in the second direction by the actuator so as to urge the workpiece in lateral translation across the flow path and perpendicular to the first direction according to repositioning instructions from the processor in response to the position information from the sensor as the workpiece simultaneously translates in the first direction downstream along the flow path across the running element while frictionally engaged by the running element.
The running element has a length in the first direction which does not exceed the length of the lug space of the lugs on the lugged conveyor.
In one embodiment, the running element is at least one ending roll, which may be a first array of ending rolls extending in the second direction across the flow path. The at least one ending roll may include a plurality of ending rolls spaced apart in a downstream array from a first upstream ending roll, each ending roll of the plurality of ending rolls independently actuable for increasingly accurate repositioning of the workpiece as the workpiece is translated downstream into sequential frictional engagement with successive downstream ending rolls of the plurality of ending rolls. The at least one ending roll may also include a plurality of arrays of ending rolls wherein each array of ending rolls in the plurality of arrays of ending rolls is an array of ending rolls extending in the second direction across the flow path, and wherein the plurality of arrays of ending rolls are spaced apart in a downstream array from a first upstream array of ending rolls. In this embodiment each array of ending rolls of the downstream array is independently actuable for increasingly accurate repositioning of the workpiece as the workpiece is translated downstream into sequential frictional engagement with successive downstream arrays of ending rolls of the downstream array.
In a further embodiment the at least one running element includes a pair of running elements disposed oppositely on upper and lower sides of the workpiece flow path, the pair of running elements vertically spaced apart for pinching the workpiece between the pair of running elements. The pair of running elements may be a pair of rollers. The pair of running elements may include at least one hold-down roll on the upper side of the flow path and at least one ending roll on the lower side of the flow path. The at least one hold-down roll urges the workpiece down onto the at least one ending roll. Again, the at least one ending roll may be a first array of ending rolls extending in the second direction across the flow path, and may include a plurality of ending rolls or arrays of ending rolls spaced apart in a first downstream array from the first upstream ending roll or first array of ending rolls. The at least one hold-down roll may include a plurality of hold-down rolls spaced apart in a second downstream array corresponding to the first downstream array.
The apparatus of the present invention may include a frame having upper and lower arms for extending across the flow path. The pair of running elements may be a pair of upper and lower arrays of wheels oriented in the first direction, where the arrays of wheels are mounted respectively to the upper and lower arms of the frame. The actuator selectively translates the frame in the second direction so as to actuate the pair of running elements in the second direction whereby the workpiece is pushed or pulled in the second direction by the pair of running elements. The frame may be a xe2x80x9cCxe2x80x9d-shaped frame. The upper and lower arms may extend in the second direction respectively above and below the flow path, a vertical arm joining the upper arm to the lower arm adjacent a side edge of the conveyor.
In a further embodiment, the pair of running elements may be a pair of upper and lower endless belts or chains oriented in the first direction, the endless belts or chains mounted respectively to the upper and lower arms of the frame. Again, the actuator selectively translates the frame in the second direction so as to actuate the pair of running elements in the second direction whereby the workpiece is pushed or pulled in the second direction by the pair of running elements.
The pair of running elements may include a plurality of pairs of running elements spaced apart in a downstream array from a first upstream pair of running elements. Again, each pair of running elements of the downstream array are independently actuable in the second direction for increasingly accurate repositioning of the workpiece as the workpiece is translated downstream into sequential frictional engagement with successive downstream pairs of running elements. Thus for example the pair of upper and lower arrays of wheels may include a plurality of the pairs of upper and lower arrays of wheels spaced apart in a downstream array from a first upstream pair of upper and lower arrays of wheels.